Many studies on the use of magnetic particles as bio-related materials have recently been attempted. Magnetic particles started to be frequently used as basic materials in bioengineering research, and have been used for the rapid and simple isolation of biomaterials. Conventional methods for the isolation of biomaterials, particularly, nucleic acids, are processes requiring large amounts of time and labor, and comprise several extraction and centrifugation steps, but the yield and purity of nucleic acids isolated by these methods were low, and these methods were not suitable for the automated or high-throughput isolation of biomaterials. However, in recent studies, special magnetic particles were prepared, and methods of rapidly and efficiently isolating nucleic acids using magnetic particles under suitable buffer conditions were developed (U.S. Pat. Nos. 5,523,231 and 5,665,554). In addition, the use of the above methods for nucleic acid isolation can provide an automated method capable of isolating nucleic acids by treating a large number of samples at the same time. For example, the use of an automated robotic system can isolate a large amount of a desired nucleic acid by automatically treating several hundred or thousand samples.
Isolation of nucleic acids (DNA and RNA) from biological samples is the most important step in biochemical research and diagnostic processes. If isolation of genetic materials from samples is not performed, gene detection, gene cloning, gene sequencing, gene amplification, cDNA synthesis or the like, which is the next step, cannot be performed. To isolate DNA or RNA from various cell mixtures, an effective and reproducible isolation method is required. Thus, isolation methods employing magnetic particles have recently been developed. The method of isolating nucleic acids using magnetic particles comprises inducing the binding of magnetic particles to a gene, and then applying an external magnetic field to the sample to isolate the nucleic acid. It is generally known that the particle size of magnetic particles that are used for the isolation and purification of DNA, RNA, protein or the like is preferably in the range from about 100 nm to about 10 μm.
In order to use magnetic particles for the isolation and purification of genes (nucleic acids) or proteins as described above, a functional group capable of binding to a gene or a specific protein should be conjugated to the surface of the magnetic particles. For this purpose, the magnetic particles should be coated with an organic functional group or silica.
Typical examples of the above-described magnetic particle materials that are used for isolation of biomaterials such as nucleic acids include magnetic iron oxide particles. Magnetic iron oxide particles are generally present as magnetite (Fe3O4), maghemite (Fe2O3) or hematite (Fe2O3), and can be used for the isolation and purification of biomaterials, for example, nucleic acids (DNA and RNA), proteins, peptides and polypeptides, as well as lipids.
In conventional methods for preparing magnetic particles for isolating nucleic acids, magnetic particles, which do not aggregate and interact with one another, can be prepared only when magnetic iron or iron oxide particles are prepared from an iron salt compound by a liquid-phase reduction method and are coated with silica, a polymer or a nonmagnetic material such as gold or silver. In recent years, among such magnetic particles, silica-coated magnetic particles have been mainly developed (U.S. Pat. Nos. 6,027,945, 6,673,631, and 7,183,002, and Japanese Patent No. 3253638). However, such silica-coated magnetic particles have shortcomings in that a process for preparing the silica-coated magnetic particle is complex and the yield of isolation of biomaterials such as nucleic acids by the silica-coated magnetic particles is low.
Accordingly, the present inventor have found that, when a method for the chemical preparation of silica magnetic particles comprises using a silane treatment process and adding an acid-base catalyst to an alcohol solvent to induce a silica formation reaction, it can prepare highly active silica magnetic nanoparticles, thereby completing the present invention.